A recent study published in Nature Microbiology has found that a range of industrial and agricultural chemicals can affect the balance of human gut bacteria. The research team tested 1,076 different compounds commonly used in agriculture and industry, including pesticides, fungicides, flame retardants, and plastic additives.
The study focused on how these chemicals interact with 22 types of bacteria that are often found in a healthy human gut. Researchers exposed these bacteria to each chemical for 24 hours and measured their growth. They found that 168 chemicals were able to inhibit the growth of at least one bacterial strain. Bacteroidales, especially Parabacteroides distasonis, were most affected by these chemicals. On the other hand, Akkermansia muciniphila and Escherichia coli showed more resistance.
Fungicides and industrial chemicals were among those with the strongest antimicrobial effects. About one-third of fungicides and industrial compounds tested had inhibitory effects on gut bacteria. Some substances such as closantel (an antiparasitic), bisphenol AF (used in plastics), tetrabromobisphenol A (a flame retardant), emamectin benzoate (an insecticide), fluazinam (a fungicide), and chlordecone (an insecticide) showed broad-spectrum inhibition.
Researchers also observed that some chemicals changed the composition of bacterial communities when tested together rather than individually. For example, while Eubacterium rectale was sensitive to BPAF when isolated, it was protected within a community setting.
To understand how certain bacteria develop tolerance to pollutants, scientists used genetic screening methods with mutant libraries in species like Parabacteroides merdae. They identified genes related to efflux pumps—mechanisms bacteria use to remove harmful substances—as important for resisting both chemical pollutants and antibiotics such as ciprofloxacin.
"Loss of this regulator increased tolerance to multiple pollutants and also conferred increased resistance to the antibiotic ciprofloxacin, highlighting potential links between pollutant exposure and antibiotic resistance through shared tolerance and efflux pathways," according to the study authors.
The researchers concluded that many interactions between common chemicals and gut microbes remain undocumented. "In sum, the study identified 588 inhibitory interactions between 168 chemicals and human gut bacteria, most of which were not previously known to have antibacterial properties."
While laboratory conditions allowed precise control over concentrations and exposures, further research is needed outside the lab environment. The authors note: "However, the experiments were conducted in vitro at defined concentrations, and further in vivo and epidemiological studies are needed to determine whether similar effects occur under real-world human exposure conditions and to define relevant exposure levels."
